1. Field of the Invention
The present invention relates to a method for preparing nanoporous carbons with enhanced mechanical strength and the nanoporous carbons prepared by the method, and more specifically, to a method for preparing a nanoporous carbon, comprising the steps of (i) synthesizing a mesoporous silica template not being subjected to any calcination process; (ii) incorporating a mixture of a monomer for addition polymerization and an initiator, or a mixture of a monomer for condensation polymerization and an acid catalyst into the as-synthesized mesoporous silica template, and reacting the mixture to obtain a polymer-silica composite; and (iii) carbonizing the polymer-silica composite by heating it at a high temperature to obtain a carbon-silica composite, from which the silica template is then dissolved in a solvent.
2. Description of the Prior Art
Porous materials allowing fluids to flow therethrough can be classified by their pore sizes. Very small pores having diameters less than 2 nm called micropores, while very large pores (>50 nm) are called macropores. Pores of intermediate size between 2 and 50 nm are called mesopores. Among them, materials having mesopores have attracted considerable attention because they have pores that are large enough to readily allow liquids to enter the materials and provide liquid access to more surface area per unit volume of materials than either microporous or macroporous materials. In particular, nanoporous carbons, one type of the mesoporous materials, become the center of attention because they are synthesized from various precursors and have a variety of applications, such as catalysts, catalyst supports, separating agents, hydrogen reserving materials, adsorbents, membranes and membrane fillers.
In the conventional process, nanoporous carbon materials have been prepared from a mesoporous silica or alumina template obtained by using a surfactant, which is then removed through calcinations of the template. After calcinations, carbon precursors are introduced into the template and carbonized to produce a carbon-template composite, from which the template is dissolved with a certain solvent and removed [See: R. Ryoo, S. H. Joo and S. Jun, J. Phys. Chem. B, 1999, 103, 7743; S. H. Yoon, T. Hyeon, S. M. Oh and K. B. Kim, Chem. Commun., 1999, 2177; S. B. Yoon, J. Y. Kim and J. S. Yu, Chem. Commun., 2001, 559; S. Jun, S. H. Joo, R. Ryoo, M. Kruk and M. Jaroniec, J. Am. Chem. Soc., 2000, 122, 10712]. The conventional method is desirable in terms of obtaining the carbon structure with various pore size, but, disadvantageously, its production cost is high due to the additional calcination. Besides, since the pore size in the template become considerably reduced and irregular in the calcinations, the resultant carbons have the thinner walls so their mechanical stability could be deteriorated and thus their lower strength may limit the use of the carbon.
Accordingly, in the field, there are strong reasons for exploring and developing an improved method of preparing nanoporous carbons having uniform-sized mesopore, high surface area and high mechanical stability through a simple process at low production cost.